从分离一个shared_ptr的指针？ [英] Detach a pointer from a shared_ptr?

问题描述

  

可能重复：结果
  如何释放从boost ::指针shared_ptr的？

我的界面的函数返回一个指向对象。用户应该采取对象的所有权。我不想返回Boost.shared_ptr，因为我不希望强制客户端使用升压。但是在内部，我想指针存储在一个shared_ptr至prevent内存泄漏等异常的情况下，似乎有没有办法从一个共享指针分离的指针。这里任何想法？

解决方案

什么你要找的是一个发布功能; 的shared_ptr 不具有释放功能。 ％的提升手动：

  

Q值。为什么shared_ptr不提供一个release（）函数？

  
  

一个。的shared_ptr不能放弃所有权除非它是唯一的（），因为其它拷贝仍然销毁对象。

  
  

考虑：

 的shared_ptr＆LT; INT＆GT;一个（新int）;在
shared_ptr的＆LT; INT＆GT; B（A）; // a.use_count（）== b.use_count（）== 2为int * p = a.release（）;//现在谁拥有P + b仍然会调用析构函数删除就可以了。
 

  

此外，通过释放（）返回的指针将难以可靠地释放，作为源的shared_ptr可能已被用定制删除创建

两个选项，你可能会考虑：

• 您可以使用的std :: TR1的:: shared_ptr的，这就需要你的用户使用C ++库实现支持TR1的或的使用促进;至少这会给他们两者的选项。


• 您可以实现自己的的boost :: shared_ptr的式的共享指针，并使用你的外部接口。

您也可以看一下在讨论关于<一个这个问题， href=\"http://stackoverflow.com/questions/335330/using-boostsharedptr-in-a-librarys-public-interface\">using提高:: shared_ptr的一个库的公共接口。

Possible Duplicate:
How to release pointer from boost::shared_ptr?

A function of my interface returns a pointer to an object. The user is supposed to take ownership of that object. I do not want to return a Boost.shared_ptr, because I do not want to force clients to use boost. Internally however, I would like to store the pointer in a shared_ptr to prevent memory leaks in case of exceptions etc. There seems to be no way to detach a pointer from a shared pointer. Any ideas here?

解决方案

What you're looking for is a release function; shared_ptr doesn't have a release function. Per the Boost manual:

Q. Why doesn't shared_ptr provide a release() function?

A. shared_ptr cannot give away ownership unless it's unique() because the other copy will still destroy the object.

Consider:

shared_ptr<int> a(new int);
shared_ptr<int> b(a); // a.use_count() == b.use_count() == 2

int * p = a.release();

// Who owns p now? b will still call delete on it in its destructor.

Furthermore, the pointer returned by release() would be difficult to deallocate reliably, as the source shared_ptr could have been created with a custom deleter.

Two options you might consider:

• You could use std::tr1::shared_ptr, which would require your users to use a C++ library implementation supporting TR1 or to use Boost; at least this would give them the option between the two.
• You could implement your own boost::shared_ptr-like shared pointer and use that on your external interfaces.

You might also look at the discussion at this question about using boost::shared_ptr in a library's public interface.

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